Flu season consistent with previous years

With flu season coming around, general trends of the illness are in line with previous years of reporting without any noticeable change in the number of cases in the greater Hanover area, said Dartmouth-Hitchcock Medical Center professor of immunology Richard Enelow.

The last major outbreak was during the 2009-2010 school year, which correlated with the swine flu pandemic.

“It looks like most of the country has pretty widespread flu activity, which is not that unusual for the time of year,” Enelow said. “It doesn’t appear to be a bad year for highly virulent strains.”

Enelow discussed at length the challenges that the flu presents as a virulent disease.

As a virus, the flu constantly mutates its surface protein, known as hemagglutinin, rendering vaccinations from years prior nearly useless, as the antibodies that the immune system had already produced in response to prior vaccines are no longer effective.

One different subtype of hemagglutinin is H1N1, most commonly referred to as “swine flu,” with the “H” standing for hemagglutinin class 1 and the “N” standing for an additional surface protein found in influenza viruses known as viral neuraminidase.

The typical process for creating a vaccine against the flu involves determining which of the four current strains of influenza are circulating in Asia during the spring, and then deciding which of these strains will be included in the vaccine, Enelow said. This usually gives pharmaceutical companies four to six months to produce the one hundred million doses needed for the American public during the fall.

Presently, the most prevalent strain in both the nation and New Hampshire is the H3N2 strain, which originated in Hong Kong. While the American public receives constant reminders about receiving a flu shot before the onset of flu season, the general effectiveness of these vaccinations remains in question.

“About 50 percent of the time, by the time the flu’s come around, the strains have changed from what the vaccine was designed to protect against to what’s circulating,” Enelow said. “That doesn’t mean you don’t get any protection from it, but you usually only get partial protection.”

DHMC immunologist Michael Calderwood said that this would mean that on a typical college campus, 50 out of 100 vaccinated students would not get the flu if the effectiveness of the vaccine was at 50 percent. The highest effectiveness level recorded for the vaccine is 75 percent, he said.

This year, however, the vaccinations that were produced managed to include the same strains of influenza that are currently circulating, with 96 to 97 percent of the strains being H3N2, which present a direct match to the vaccine, Calderwood said. The other three percent has been identified as the H1H1 strain, which was also included in the vaccine.

Despite this, there remains an inherent variability in the vaccine’s ability to respond to infection, thereby allowing people to contract the virus even after they have received protection from it. Enelow attributes this to the general effectiveness of the vaccine at generating a potent immune response, which can vary highly from year to year. The most efficient way to generate neutralizing anti-bodies remains unclear.

Nicholas Gutierrez ’20 said that he was admitted to Dick’s House after contracting the flu on a Saturday morning and was not discharged until Tuesday. Because of Gutierrez’s asthma, the doctors at Dick’s House kept him for a longer period to ensure that he did not contract pneumonia.

“It was really sudden,” Gutierrez said. “I had a fever of 103 degrees and I was coughing. My chest felt like it was on fire when I would cough.”

Calderwood noted that the nature of college campuses made them more susceptible to viral infections, due to the students’ close proximity. Students with underlying conditions that compromise their immune systems, such as asthma, are more susceptible to being further compromised by influenza.

“Any illnesses spread by droplets or respiratory illnesses are more likely to have an outbreak,” Calderwood said.